The median age of mothers for all births registered in 2009 was 30.6 years. The median age of women who gave birth in a nuptial relationship was 31.7 years, almost five years older than those who gave birth in an ex-nuptial relationship (27.1 years). Of those who gave birth in an ex-nuptial relationship, the median age of women where paternity was not acknowledged (25.2 years) was lower than where paternity was acknowledged (27.3 years).

Until the 1930s, the median age of mothers giving birth was decreasing. During the 1930s, the median age stabilised, then rose briefly at the end of the Second World War, with an equally sharp decline immediately following the war. The median age of mothers fell substantially over the following three decades, reaching a low of 25.4 years in 1971. The reinterpretation of abortion law in New South Wales in 1971 was associated with a substantial fall in births to young women and an increase in the median age of mothers. From 1972, the median age of mothers consistently increased, reaching 30.8 years in 2006, the highest on record.

However, data quality investigations during processing of 2007 birth registrations data indicated that age of parents, and therefore median age, may have been slightly overstated for some birth registrations in 2006 and previous years (see paragraph 49 of the Explanatory Notes for more information). Despite the uncertainty associated with information on age of mother, the increases in median age of mother apparent since the early 1970s appear to have halted. In 2007 and 2008, the median age remained at 30.7 years, and in 2009 the median age decreased to 30.6 years, the lowest median age recorded since 2004.

2.6 Median age of parents, Australia - 1929 to 2009

The median age of fathers has also followed an upward trend since the 1970s. In 2009, the median age of fathers was 33.0 years. The median age of fathers excludes information from births where paternity is not acknowledged (10,000 births in 2009). Data quality investigations during 2007 processing indicated that age of parents, and therefore median age of fathers, may have been slightly overstated for some birth registrations in 2006 and previous years (see paragraph 49 of the Explanatory Notes for more information).

Between 1989 and 2009, the median age of fathers of nuptial births increased by almost three years, from 31.2 to 34.0 years, while the median age of fathers of ex-nuptial births, who acknowledged the birth of their child, also increased, from 27.2 years to 29.9 years.